1. Field of the Invention
The present invention relates to an air conditioning system suitable for use in an electric vehicle, and more specifically to such an air conditioning system which is capable of energizing a glass heating means for heating a front or rear window glass in preference to the energization of a space air conditioning mechanism when the front window glass, the rear window glass, etc. are in an iced or foggy state.
2. Description of the Related Art
The concept of mounting an air conditioner in a vehicle and controlling temperature, humidity, airflow, etc. inside of the vehicle so as to ensure comfortable driving, has heretofore been effected. Also, an apparatus for removing water or moisture condensed on the front and rear windows with electric resistance heaters or the like incorporated in the glass and avoiding an iced state of each of the front and rear windows, has widely been used to permit safe driving of the vehicle.
When the vehicle is an electric vehicle, for example, the limited or finite energy available should be effectively used. However, when the air conditioner and the heater incorporated into each window glass or the like as described above are simultaneously activated, for example, the energy used is temporarily increased, thereby causing a problem that the running or driving range distance of the vehicle and the running speed thereof are greatly restricted.
An air conditioner suitable for an electric vehicle has been proposed in Japanese Laid-Open Publication No. 2-220913, for example. In that proposal, the technical idea of using an inverter for controlling a motor used to drive a compressor for an air conditioner irrespective of the motor used for the running of the vehicle, has been disclosed. The number of rotations of the compressor driving motor can be changed according to cooling and heating loads under the control of the inverter. Therefore, the compressor can provide the required cooling and heating ability as needed. In the existing technical idea, however, a problem of excess energy usage occur when the air conditioner and heating means for the two pieces of front and rear window glass are simultaneously energized, and no solution has yet been proposed although the compressor itself can be effectively controlled.
Further, the technical idea how to locate a sensor or how to detect the state of dimness of a piece of front window glass or the like at the time of its detection, has been disclosed in Japanese Laid-Open Publication No. 2-304343 and Japanese Patent Publication No. 3-36180. However, the above-described problem which has been pointed out by the present applicant, is not yet definitely solved.